Does the freedom of movement spell protect a character from being stunned? The argument is that “stun” is a condition that hinders movement.
Freedom of movement is one of those tricky spells that has a lot of open-ended wording that might lead to confusion. The spell becomes much more manageable if you just look at it as something that ignores any physical impediment to movement or actions. If you assign this restriction, then it makes sense that freedom of movement works against solid fog, slow, and web; each of these spells puts something in the way of the creature that stops them from moving/acting, or specifically targets the creature’s physical movement.
With this interpretation, spells and effects such as hold person that apply a mental impediment to taking any action would not be bypassed by freedom of movement. These are mental effects, and freedom of movement only helps you bypass physical effects (such as solid fog) or effects that specifically impede just your movement, not spells that stop you from taking any action, as hold person does.
In the same vein, freedom of movement would not work on someone who had been turned to stone by a medusa’s gaze or by a flesh to stone spell.
To answer the original question, being stunned is one of those mental effects and would normally deny a creature the ability to act at all. Since it’s not specifically focused on just impeding movement, and it is a mental, not physical impediment, freedom of movement would not help a stunned
creature to act or move normally.
This interpretation of freedom of movement can make it easier to adjudicate the effects of the spell, but it is also more restrictive. As always, it will ultimately be up to the Dungeon Master to make the best call as he sees fit for his campaign and play session.